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| author | Tanaka Akira <[email protected]> | 2024-06-02 10:17:36 +0900 |
|---|---|---|
| committer | Tanaka Akira <[email protected]> | 2024-06-02 10:17:57 +0900 |
| commit | d03c61241a38cb16ed185d609af2d3dc69f66ba3 (patch) | |
| tree | 233d4fdd60363ca6a911c2a7159fa5c83f64f263 /timev.rb | |
| parent | 0cc5f77c07d964bb308e29ecb8e5b4ee81aa26d1 (diff) | |
Time internal representation described.
Diffstat (limited to 'timev.rb')
| -rw-r--r-- | timev.rb | 36 |
1 files changed, 36 insertions, 0 deletions
@@ -45,6 +45,42 @@ # (for example, by method Time.now) # has the resolution supported by the system. # +# == \Time Internal Representation +# +# Time implementation uses a signed 63 bit integer, Integer(T_BIGNUM), or +# Rational. +# It is a number of nanoseconds since the _Epoch_. +# The signed 63 bit integer can represent 1823-11-12 to 2116-02-20. +# When Integer or Rational is used (before 1823, after 2116, under +# nanosecond), Time works slower than when the signed 63 bit integer is used. +# +# Ruby uses the C function "localtime" and "gmtime" to map between the number +# and 6-tuple (year,month,day,hour,minute,second). +# "localtime" is used for local time and "gmtime" is used for UTC. +# +# Integer(T_BIGNUM) and Rational has no range limit, +# but the localtime and gmtime has range limits +# due to the C types "time_t" and "struct tm". +# If that limit is exceeded, Ruby extrapolates the localtime function. +# +# "time_t" can represent 1901-12-14 to 2038-01-19 if it is 32 bit signed integer, +# -292277022657-01-27 to 292277026596-12-05 if it is 64 bit signed integer. +# However "localtime" on some platforms doesn't supports negative time_t (before 1970). +# +# "struct tm" has tm_year member to represent years. +# (tm_year = 0 means the year 1900.) +# It is defined as int in the C standard. +# tm_year can represent between -2147481748 to 2147485547 if int is 32 bit. +# +# Ruby supports leap seconds as far as if the C function "localtime" and +# "gmtime" supports it. +# They use the tz database in most Unix systems. +# The tz database has timezones which supports leap seconds. +# For example, "Asia/Tokyo" doesn't support leap seconds but +# "right/Asia/Tokyo" supports leap seconds. +# So, Ruby supports leap seconds if the TZ environment variable is +# set to "right/Asia/Tokyo" in most Unix systems. +# # == Examples # # All of these examples were done using the EST timezone which is GMT-5. |